• The Transactions of the Korea Information Processing Society
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• v.3 no.7
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• pp.1917-1923
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• 1996

The reliability of the multiple-disk system is degraded as the number of disks are increased. In this paper, we find the reliability, in terms of MTTF (Mean Time To Failure)of the single-disk-failure-tolerant disk systems in which the distributions of repair times of failed disk are heterogeneous and general. Also, we derive thresholds of the design parameters such as the mean of life time and repair time, and we consider the cost minimization problem in the special cases under a linear cost structure and constraints to the life of the disk system.

• International Journal of Reliability and Applications
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• v.11 no.2
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• pp.89-106
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• 2010

This paper deals with the reliability and availability characteristics of three different series system configurations with warm standby components and a repairable service station. The failure time of the primary and warm standby are assumed to be exponentially distributed with parameters ${\lambda}$ and ${\alpha}$ respectively. The repair time distribution of each server is also exponentially distributed with parameter ${\mu}$. The breakdown time and the repair time of the service station are also assumed exponentially distributed with parameters ${\gamma}$ and ${\beta}$ respectively. We derive the reliability dependent on time, availability dependent on time, the mean time to failure, $MTTF_i$, and the steady-state availability $A_i$(${\infty}$) for three configurations and perform comparisons. Comparisons are made for specific values of distribution parameters and of the cost of the components. The three configurations are ranked based on: $MTTF_i$, $A_i$(${\infty}$), and $C_i/B_i$ where $B_i$ is either $MTTF_i$ or $A_i$(${\infty}$).

• Journal of Applied Reliability
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• v.14 no.1
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• pp.1-9
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• 2014

One important measure of performance for a repairable system is steady-state availability. In this paper, a method to estimate and establish confidence interval for the steady-state availability under Weibull lifetime and lognormal repair time distributions is proposed. Also, bias and mean squared error of a point estimator for an availability are investigated. In addition, a procedure to derive the sample size and critical value for availability demonstration test is presented and illustrated with a numerical example.

• Journal of the Korean Arthroscopy Society
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• v.13 no.1
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• pp.72-76
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• 2009

Two diabetes mellitus patients treated by arthroscopy and associated procedure for an infection after arthroscopic rotator cuff repair were involved. The time interval from rotator cuff repair to symptom development was 18 days in average and arthroscopic debridement and associated procedure for infection applied in average 65 days after symptom development. Patient evaluation was done according to the KSS, ASES, UCLA and Constant Score. We used antibiotics for average 22.5 days after arthroscopic debridement and associated procedure, the infection was treated in average 4 months. At final follow-up, the mean KSS score was 82 points, the mean UCLA score was 33 points, the mean ASES score was 91 points, the mean Constant score was 71 points. All infections following arthroscopic rotator cuff repair were cured by arthroscopy and associated procedure. ROM and functional results were much improved, the pain and satisfaction were also much improved.

• Journal of Korean Foot and Ankle Society
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• v.23 no.3
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• pp.100-104
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• 2019

Purpose: This study examined the clinical outcomes and assessed the average time to return to play following a peroneal tendon repair in Korean athletes. Materials and Methods: Between March 2004 and February 2017, a total of 30 athletes underwent peroneal tendon repair for a peroneal tendon tear. The indications of surgical treatment were chronic pain or intractable symptoms after a previous ankle sprain affecting sports activity refractory to conservative treatment for at least six months. The patient underwent tubulization for a longitudinal tendon rupture. Peroneus longus to peroneus brevis tenodesis was performed when tendon repair was impossible due to total rupture or multiple longitudinal rupture. Results: Twenty patients not included in this study were as follows: insufficient follow-up, previous surgery, and additional bone surgery. All 10 patients had a previous ankle sprain history, tenderness and swelling on the retromalleolar area. In the 10 patient population, there were five peroneus brevis tendon tears, three peroneus longus tendon tears, one peroneus longus and brevis tendon tear, and one peroneus brevis and superior peroneal retinaculum tear. In the 10 patients, six cases of peroneal brevis tendon repair and four cases of peroneal longus to brevis tenodesis were performed. The preoperative American Orthopaedic Foot and Ankle Society score was improved from a mean of 60.6 (standard deviation [SD], 8.64) to a mean of 90.2, postoperatively (SD, 4.4; p<0.012). The preoperative visual analogue scale was improved from a mean of 5.43 (SD, 1.2) to 0.5 (SD, 0.16), postoperatively (p<0.023). The mean length of time to return to play was 12.2 weeks (range, 8~16 weeks). Conclusion: Peroneal tendon tear can occur due to sports injuries. If there is tenderness at the retromalleolar area, the surgeon should consider a peroneal tendon lesion. Surgical repair of the peroneal tendon can be an effective treatment to help athletes to return to play.

• Journal of Chest Surgery
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• v.50 no.6
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• pp.430-435
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• 2017

Background: Mycotic aortic aneurysms are rare and life-threatening. Unfortunately, no established guidelines exist for the treatment of patients with mycotic aortic aneurysms. The purpose of this study was to evaluate the midterm outcomes of the open repair of mycotic thoracic and thoracoabdominal aneurysms and suggest a therapeutic strategy. Methods: From 2006 to 2016, 19 patients underwent open repair for an aortic aneurysm. All infected tissue was extensively debrided and covered with soft tissue. We recorded the clinical findings, anatomic location of the aneurysm, bacteriology results, antibiotic therapy, morbidity, and mortality for these cases. Results: The median age was $62{\pm}7.2years$ (range, 16 to 78 years), 13 patients (68%) were men, and the mean aneurysm size was $44.5{\pm}4.9mm$. The mean time from onset of illness to surgery was $14.5{\pm}2.4days$. Aortic continuity was restored in situ with a Dacron prosthesis (79%), homograft (16%), or Gore-Tex graft (5%). Soft-tissue coverage of the prosthesis was performed in 8 patients. The mean follow-up time was $43.2{\pm}11.7months$. The early mortality rate was 10.5%, and the 5-year survival rate was $74.9%{\pm}11.5%$. Conclusion: This study showed acceptable early and midterm outcomes of open repair of mycotic aneurysms. We emphasize that aggressive intraoperative debridement with soft-tissue coverage results in a high rate of success in these high-risk patients.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.539-544
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• 2004

In this paper, we present reliability modeling and analysis method of the Automated Guideway Transit(AGT) vehicle system using analytical models, based on Markov Chains. The Markov model can express state transition of the AGT vehicle sys. that is considered to be in one of four states, such as basic operating (0), minor delay(1), major delay(2) and non-operating(3) state. The proposed Markov model is illustrated with a numerical example and cases to find a steady state availability, MTBF(mean time between failures), and MTTR(mean time to repair) under specified failure and repair rate arc demonstrated.

• Journal of Cardiovascular Imaging
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• v.30 no.1
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• pp.50-58
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• 2022

BACKGROUND: Little is known regarding right ventricular (RV) remodeling immediately after Tetralogy of Fallot (TOF) repair. We sought to describe myocardial deformation by cardiac magnetic resonance imaging (CMR) after TOF repair and investigate associations between these parameters and early post-operative outcomes. METHODS: Fifteen infants underwent CMR without sedation as part of a prospective pilot study after undergoing complete TOF repair, prior to hospital discharge. RV deformation (strain) was measured using tissue tracking, in addition to RV ejection fraction (EF), volumes, and pulmonary regurgitant fraction. Pearson correlation coefficients were used to determine associations between both strain and CMR measures/clinical outcomes. RESULTS: Most patients were male (11/15, 73%), with median age at TOF repair 53 days (interquartile range, 13,131). Most patients had pulmonary stenosis (vs. atresia) (11/15, 73%) and 7 (47%) received a transannular patch as part of their repair. RV function was overall preserved with mean RV EF of 62% (standard deviation [SD], 9.8). Peak radial and longitudinal strain were overall diminished (mean ± SD, 33.80 ± 18.30% and -15.50 ± 6.40%, respectively). Longer hospital length of stay after TOF repair was associated with worse RV peak radial ventricular strain (correlation coefficient (r), -0.54; p = 0.04). Greater pulmonary regurgitant fraction was associated with shorter time to peak radial RV strain (r = -0.55, p = 0.03). CONCLUSIONS: In this small study, our findings suggest presence of early decrease in RV strain after TOF repair and its association with hospital stay when changes in EF and RV size are not yet apparent.

• Proceedings of the KSME Conference
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• 2001.06a
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• pp.585-590
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• 2001

Turbine blade is subject to torsional load by torsion-mount, centrifugal load by rotation of rotor and repeated bending load by steam pressure. Turbine with partially cracked blade has normal working condition at initial repair time but vibratory working condition at middle repair time due to crack growth. Finite element analysis on turbine blade indicates that repeated bending load out of all loads is the most important factor on fatigue strength of turbine blade. Therefore, this study shows root mean square roughness has linear relation with stress intensity factor range in 12% Cr steel and can predict loading condition of fractured turbine blade.

• Transactions of the Korean Society of Automotive Engineers
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• v.9 no.6
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• pp.170-177
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• 2001

Turbine blade is subject to torsional load by torsion-mount, centrifugal load by rotation of rotor and repeated bending load by steam pressure. Turbine with partially cracked blade has normal working condition at initial repair time but vibratory working condition at middle repair time due to crack growth. Finite element analysis on turbine blade indicates that repeated bending load out of all loads is the most important factor on fatigue strength of turbine blade. Therefore, this study shows root mean square roughness has linear relation with stress intensity factor range in 12% Cr steel and can predict loading condition of fractured turbine blade.